Sockets.cpp: Fix initialization of UDD socket
Sockets.cpp: Fix initialization of UDD socket

Without this line, destination address for a UDD socket is left with
incorrect value AF_UNSPEC. Later on when calling DatagramSocket:write(),
sendto() fails with EINVAL.

This commit fixes test SocketsTest.cpp.

Change-Id: I6e1b7e743a781abdcf69aa9842b30be893633433

osmocom/osmo-trx,osmocom/osmo-trx,ttsou/osmo-trx,ttsou/osmo-trx,osmocom/osmo-trx,ttsou/osmo-trx,ttsou/osmo-trx,osmocom/osmo-trx